Preloaded safety spring unit



June P. E. REEvEs ETAL PRELOADED SAFETY SPRING UNIT 'Filed Aprl 5. 1940 Patented June 23, 1942 UNITED STATS ital 2j;

ai" oelcs I PRELOADED SAFETY SPRING UNI'Il` Application April 5, 1940, Serial No. 328,012

8 Claims.

The present invention relates to a pre-loaded spring unit, and to the combination of that unit with a particular kind of variable speed drive mechanism.

Within the past few years, the type of Variable speed drive illustrated in Patent No. 1,822,935, and the type of drive illustrated in Patent No. 2,189,711, have gained wide popularity. Such drives incorporate what has come to be known as a resiliently expansible V-pulley, which consists of a coned disc fixed to a rotatable element, a mating coned disc axially slidable with respect to the fixed disc, and a spring urging the slidable disc toward the fixed disc. As the slidable disc moves outwardly against the effect of the spring, the degree of force exerted by the spring, of course, increases. It is desirable that relatively heavy spring pressure be applied to the shiftable disc; but that the degree of that pressure shall vary only slightly between the extreme positions of the disc. The force exerted by a short, stiff spring would vary rather widely within the limits of movement of theshiftable disc; and therefore, it has been customary to use a long, relatively soft spring, Dre-compressed to desired length and effective pressure. When such a spring is used, the degree of pressure exerted thereby upon the disc varies only slightly Within the limits of movement of the disc.

Rather heavy spring pressures are used in units of this character, and particularly in the larger sizes thereof; and, since there is nothing about the appearance of a spring to indicate to the observer whether or not that spring is partially` collapsed from its relaxed position, a spring such as that illustrated in either of the patents above mentioned is potentially dangerous to operators of the machine. If an operator, unacquainted with the fact that the spring of the unit under consideration is loaded, incautiously removes the abutment nut, that nut will fly away from the unit, when it is backed olf of the nal thread, with an enormous velocity; and industrial accidents have occurred as a result of this situation.

It is the primary object of the present invention to overcome the possibility of such accidents, and to render a pre-loaded spring entirely safe in the hands of the user of the equipment. As an incidental advantage of the present invention, the spring is housed, thereby preventing clothing, ropes, the hair of an operator, and the like from being caught in the rapidly rotating coiled spring.

To the accomplishment of the above and related objects, our invention may be embodied in (Cl. 'H1-230.17)

the forms illustrated in the accompanying drawing, attention being called to the fact, however, that the drawing is illustrative only, and that change may be made in the specic constructions illustrated and described, so long as the scope of the appended claims is not violated.

Fig. 1 is a plan view of a variable speed drive of the character illustrated in Patent. No. 1,822,935, but embodying the spring unit of the present invention; p

Fig. 2 is an enlarged longitudinal section through the said spring unit;

Fig. 3 is a section through a unit of the character illustrated in Patent No. 2,089,711, embodying the spring unit of the present invention; and

Fig. 4 is a fragmental illustration of a modified form of spring unit.

Referring more particularly to the drawing and to the embodiment of the invention illustrated in Figs. l and 2 thereof, it will be seen that We have shown a motor Ill mounted upon a carriage II slidably supported upon bed I2, and movable with relation to the bed by means of a lead screw I3. On the spindle I4 of the motor I0 is mounted a pulley unit I5 comprising a coned disc lli fixed to the spindle I4 and a mating coned disc Il axially movable with respect to the disc I6.` A belt I8 drives from the pulley I5 to a flat faced pulley I9 mounted on the shaft 20 of a driven machine 2|. The spring unit of the present invention is illustrated generally by the reference number 22.

AAs is clearly shown in Fig. 2, the disc I6 is preferably provided with an elongated hub 23 projecting from the coned face thereof, the outer end of said hub being formed with screw threads as at 24. The disc I1 is likewise formed with an elongated hub 25 projecting from its outer face, and said disc I'I with its hub 25 is slidably mounted upon the hub 23, being preferably held against rotation with respect to said disc I6. The outer face of the disc Il is preferably formed to provide an abutment surface 26.

A spring 2I-s provided for constantly urging the disc I1 toward the disc I6. One end of said spring 2'I is received in a housing unit 28 which, at one end, is formed with' an inturned lip 29 providing an abutment surface 30 adapted to engage the surface 26. The opposite end of said unit 28 is formed with an outturned lip 3l. The unit 28 is vtelescopically mounted within a second housing unit 32 which is formed at one end with an inturned lip 33 cooperating with the lip 3| of the housing unit 32 is closed by a head 34 secured in said housing unit by rivets 35, or the like, and preferably provided in its inner surface with a groove 36 for the reception of the adjacent end of the spring 21. As is clearly shown in Fig. 2, one end of the spring 21 bears against the lip 29, while the other end of said spring bears against the head 34.

In assembling the spring unitl 22, the housing unit 28 is introduced through the right-hand end of the unit 32 into telescopic association therewith. Thereafter, the spring 21 is entered in the composite housing, one end' beingbroughtvv to bear against the lip 29. By, suitable means, the spring 21 is now heavilyjpre-loaded"bycompressing the same, from its normalllength which;

greatly exceeds the expanded length of'the housing 28-32, to the length illustrated inFig.. 2;,

whereupon the head 34 is entered in thehousing 32 and is secured in place by its rivets 35",L or the like.

Whenl the head 341 haslbeerr firmly secured .in position, the unit. 22.' comprises:v ai heayilyf: pre,- loaded spring unit' which,howev1er, is entirely safe` in the hands of the user, since 'the springisrmly; and rigidly held againstlexpansicn beyond' the length illustrated in Fig. 2.

The head 34 is formedwithi an. axialibore .which is internally threaded'as at..37. Itisto benoted that, as shown in Fig. 2, the overalllengtli ofthe unit 22T is such that the Ythreads 311 may beengaged with the outermost threads 331 ofi the threaded portion `24 ofthe hub 23before bringing the abutment surface 301 into Contact; with the surface 26.- In other Words, the distanceiV from the'inner end- 33 of the threadedse'ction 3:12 to the remote end 30 of the housing-unit. 281v isale'ss:`

than the distance from-the outerend33 of. the threaded portion 24-of thel hub 23`It`othe1adj`a'- centsurface-26-ofvthe disc Il; But,z.as t1fe-.unt

22-isrotated'to carrythe threads-3,1 farthenontd thethreads- 2'4, the surface 33 cornes intdcontact-With the-surface 26ibefore the head'i34`has.

been turned-down to itsultimate position; In-` other Words, the distance from the outermosti end-4330i the threaded portion 31 tothe remote:

end 3`0of--the housing unit28 is greaterthanethe,

distancefrom the outermost portion 38 oivthcY threads 211A tothe adjacent w surfaceY 2$ of the.

disc Il.

Thus, no resilient force need .bei overcome` to;I start the unit 22 into threadedassociation;with

the hub 23.` But, asthe unit ZZisthreadedhOme, the surface 35E comes into .contact with thelsur.- face 25` and the liply 33S. is moved; against-tha tendency of the spring 2.1, out vof` contact; with:-

the lip 3|. Thus theresilient force ofzth'eispring 2l-isapplied'to the disc- I'lV at allfftimeszafter the unit 22 is threaded',home.A But, inmemovmgithe:

unit 22' from the hub 23,2 the thleadedlengag'ement between theV unit` and .thehub.' continues".

until after the surface 30C has been inovedawazyl from-the surface 25; so that-the unit .221 istinits'.

limit.Y condition of expansionbefore. thaturrit. is

disconnected from the threads 24loff thefhfut 234 In Fig. 3, We have shown-a variable speed drive;

like thatil-lustrated inP'atentNo. 2,089'711,1.inw

corporating. a motor 53, suitably-Y mountedu upon.: the externalwalll of a casing i, Withitsspindlel 525 located 'within said-casing. i Aldisc 51H5. xedi tothe spindle 52, while a-disc 54 isiax-ially-mov- A-blt' 58 forms a driving connection between .the

discs 53 and 54 and a pulley consisting of a disc 59 xed to a shaft 60 and a disc 6I axially shiftable with respect thereto. A spring unit 22, identical in all respects with the unit illustrated in Fig. 2, has its head 34 threadedly mounted upon the threaded portion 63 of the hub 62 of the disc 59.

In Fig. 4, we have illustrated an obvious modification of the spring uniti 22.' According' to this modification, the housing unit 32 is closed at one end by a head 34 suitably secured in place byrivets 35' or the like, while the other end thereof visformed with an inturned lip 33'. The head 34' is adapted to bear against the surface 26" of"tl1e"pul1ey`disc l'l; and a housing unit 28 is teles'cop'ically" mounted within the unit 32', being formed'with an outturned lip 3l' cooperatingwith thelipi 335. The unit 28 is provided with an inturned lip 30 of suiiicient axial thickness to'permit the formation therein of threads 31 cooperable Withithev threads;24' of.v the hub 23 of pulley disclf'.

We claim:

1. In a variable speed device, a shaftpapulley, mountedon .said shaftV and' comprising al coned discl'xed .tosaid shaft and Y havingl an velongated hub projecting from itsl coned: face, a' mating coned; discl slidablyfmounted:on;said".hub,. a' tubular*v casing 4xedl'yfsecured'bnsaid hub: and: spaced'. from,v the coned face: of; saidirstr disci by. said. seconddisc', a: second tubularfcasingftelescopically associated.withsaidarst-named casing' andzbearingonisaid secondnamed disc, ar.coiled'spr.ing4 received'.- within vsaid telescoping 'casings and urgving. separation thereofland'. means. limiting; the.

degree" offseparation of. saidcasings-r the abut:- ment for. one end-fof said spring. beingzaxially removably. associatedifwitlrone ofi saidica'sings;`

2'. In; a. variabie'ispeed device,v ashaft; azpulley mounted: on; said-Y shaft; and! comprising. a: coned? disci: x'edito; said: shaftzland having; an' elongated" hub. projecting fromv its.: ccne'dfv face, a. mating coneddi'sc sii'dably mounted; on sailifhubgda tubular: casing .fxedly securedsicn-:said hub andzspa'ced:

vfrom` the. coned: face; of.' said; first' disc; by; said second" disc,.. secondiv tubolari casing-. telescopically associatedwiithtsaidirstsnamedicasing and". bearingorisaid':secondnamed disc, acotiedspring receivedvvithin saiditelesc'oping casingsfzandxurg'- ing.v separation thereof.; andLmeans/-r limitinigz'the d'egreeLcfirelativeimovemeniiofsaidcasings under' the-L influence: of 1 said'.`- springi to holdi '.sai'd. spring,` always Iunder distortingA compression; the' abut'- m'ent'; for one* end; of.' said,I spring: being a'xiallg'fi removablyfassociatediwith;one'iofsaidacasingsa 3; 5 preloadedispringcun-it comprising; a' pairoff telescoping casing;elementsgsspringabutments;ati. the remote ends; of-` said ele1nents;..andfsaidLelee ments.y being formedn ati theintelescoping fendsy to:` provide:v cooperating: means. preventing; complete: separationA otsaidelernentsin onev d`irecton-,andv a. coiled spring. received;1a,-nd; held ini. said;r unit,` bearing: against.: saict abutmentsi. and: urging; said; casing'elements to; move relatively'inf. saidone direction. one of.` said abutments; being'. axially removably;associatedV with' its. Casingnelernentsfv 4; Ai preload'edlspring :unit comprisinga .pairfof telescopingcasing elements; spring abutments' at their remote? endsiof "said: elementsg, anidfsaidr ele.- ments'. being formed at their. te'lescopingfendsitoc provide; cooperating means; preventing complete;` separation ofsaidlielement's 'in -one idirect'iong and. a coiled spring received and hel'diiinzsaidzunit; bearing against saidabutment'szand: urging said casing elementsy to move? relatively ini said fone.:

direction, the normal length of said spring being greater than the extreme distance between said abutments, one of said abutments being axially removably associated with its casing elements.

5. A preloaded spring unit comprising a can having an inturned lip at one end and an outturned lip at its opposite end, a second can having an inturned lip at one end, the internal dimensions of said last-named lip corresponding substantially with the external dimensions of said rst-named can excluding said outturned lip, said rst can being telescoped within said second can, a coiled spring received Withinsaid telescoped cans, one end of said spring bearing on said firstnamed inturned lip, and a head secured in place adjacent the end of said second can remote from its inturned lip and forming an abutment for the opposite end of said spring.

6. A preloaded spring unit comprising a can having an inturned lip at one end and an outturned lip at its opposite end, a second can having an inturned lip at one end, the internal dimensions of said last-named lip corresponding substantially with the external dimensions of said first-named can excluding said outturned lip, said rst can being telescoped Within said second can, a coiled spring having one end received in said telescoped cans and bearing on said first-named inturned lip, the normal length of said spring being greater than the expanded length of said telescoped cans, and a head fixed in the end of said second can remote from said first-named inturned lip and forming an abutment for the opposite end of said spring, holding said spring always under distorting compression.

7. The combination with an expansible pulley comprising a pair of mating, relatively axially movable coned discs, of means for resiliently urging one of said discs toward the other comprising a preloaded spring unit including a spring and two elements respectively engaging separate portions of said spring, means limiting the degree of separation of said elements, and cooperative means on one of said discs and one of said elements, mutually engageable and operative to connect said element with said disc and to adjust the relative axial positions thereof, a portion of said means on said one disc being spaced from the other of said discs a distance greater than the maximum degree of separations of said elements.

8. In combination, a rotatable' element, a coned disc fixed thereto, a mating coned disc axially slidable toward and away from said rst disc, the end of said element spaced from said rst disc by said second disc being threaded, a spring unit comprising a rst housing unit and a second housing unit telescopically axially aligned but relatively axially movable, means limiting relative movement of said units in one direction, spring abutments adjacent the remote ends of said respective units, one of said abutments being removably associated with its housing unit, and a spring bearing against said abutments and constantly resiliently urging said units to move relatively in said one direction, the abutment of one of said units being provided with an axial threaded portion cooperable with the threaded portion of said rotatable element, the distance from the adjacent end of said abutment threaded portion to the remote end of the other of said units being less than the distance from the remote end of said threaded portion of said rotatable element to the adjacent surface of said slidable coned disc, but the distance from the remote end of said abutment threaded portion to the remote end of the other of said units being greater than the distance from the remote end of said threaded portion of said rotatable element to the adjacent surface of said slidable coned disc.

, PAUL B. REEVES.

THEODORE P. KNOEDLER. 

